Exploring meteorological drivers in the transmission dynamics of viral and bacterial diarrhea: A modeling study in Davao City, Philippines.

Diarrheal diseases caused by bacterial and viral pathogens remain a significant public health concern, particularly among children under five years of age. In the Philippines, diarrhea continues to contribute substantially to childhood morbidity and mortality, with increasing evidence that meteorological conditions modulate transmission dynamics. This study examined associations between meteorological variables and diarrheal incidence in Davao City by integrating epidemiological surveillance data from 2006-2018 with meteorological records of temperature, rainfall, and relative humidity. Time-series and cross-correlation analyses identified lagged meteorological-disease relationships, revealing a statistically supported three-week lag for viral diarrhea and a biologically plausible four-week lag for bacterial diarrhea. Guided by these findings, a modified Susceptible-Infected-Recovered-Susceptible (SIRS) model was developed in which transmission rates varied with meteorological conditions. Reproduction number was derived using the Next Generation Matrix approach, and sensitivity and stability analyses were conducted to examine the influence of meteorological drivers. Results indicated that bacterial diarrhea was characterized by longer outbreaks with moderate peaks, whereas viral diarrhea exhibited shorter but higher-intensity outbreaks. Rainfall and relative humidity showed stronger associations with transmission dynamics. Stability analysis demonstrated transitions from disease-free to endemic equilibrium under fixed meteorological settings. Scenario simulations further illustrated amplified outbreak dynamics under extreme heat and heavy rainfall conditions. Overall, these findings emphasize the value of integrating meteorological-disease associations within mechanistic transmission models and highlight the importance of meteorologically informed surveillance and pathogen-specific public health planning in vulnerable urban settings such as Davao City, Philippines.